The document WO 2014/108169 A1 relates to an end cap for a bearing assembly configured to be attached to a rotatable part of the bearing. A pendulum unit is attached to the centre axis of the end cap and is adapted to oscillate between two positions under the influence of gravity such that energy can be generated by an oscillation of the pendulum unit.
Further, it is known to provide energy harvesting devices in various parts of the bearings, wherein the generator is configured to interact with a rotating target ring, encoder wheel or tone wheel such that the relative rotation of different parts of the bearing creates an oscillating current in a coil, which can be rectified for further use.
Further, it is known from other fields of technology, e.g. from watches, to use a micro generating system that converts the human movement into electric energy. Micro generating systems comprise at least an eccentric mass, a miniaturized claw pole generator, and an energy storage, wherein a gear box may be optionally provided between the eccentric mass and the generator.
The document DE 10 2006 044 562 A1 discloses a further generator unit using the oscillating gravitational force for driving a pendulum to create energy for measuring tire pressure for vehicles.
The known systems for energy harvesting based on gravitational forces in bearings have a limited scope of applicability because the oscillation amplitude of the pendulum has to be limited by stops. Further, the dynamics of the pendulum strongly depends on the centrifugal force and therefore on the speed of rotation of the bearing such that it is difficult to adapt the design of the pendulum to the intended field of application.
On the other hand, energy harvesting devices based on magnetic interaction are sensitive to external magnetic fields and the efficiency strongly depends on the precision of the gap between a rotating target ring and the yoke of a generator which is difficult to maintain in many fields of application.